1. Field of the Invention
The present invention relates to a semiconductor structure with an under bump metallization (UBM) layer and a method of fabricating the same, and more particularly to a semiconductor structure which can prevent voids in the UBM layer and a method of fabricating the same.
2. Description of the Prior Art
Modern integrated circuits are made up of millions of active and/or passive devices such as transistors and capacitors. These devices are initially isolated from each other, but are later interconnected to form functional circuits. Interconnections are increasingly determining the limits of performance and the density of modern integrated circuits. Bumps are formed on top of the interconnections so that the integrated circuit devices can be accessed.
In a typical bump formation process, a UBM layer is formed, followed by the formation of a bump on the UBM layer. The UBM layer formation includes performing a plating step to plate metal layers on the exposed portion of a metal pad. It has been found, however, that the bottom of the plated layers is rough, with voids formed therein. As a consequence, the reliability of the resulting bumps is degraded.